1. Field of the Invention
The present invention relates to a semiconductor laser device, and more particularly, to a semiconductor laser device with a high power and a manufacturing method thereof.
2. Discussion of the Related Art
Recently, with the high speed of the optical storage media such as CD-RW and DVD, there is requested a need of a laser semiconductor device with a high power.
FIG. 1 is a perspective view of a chip bar of a conventional semiconductor laser diode. A single semiconductor laser diode includes an n-type GaAs clad layer 2, an active layer 3, and a p-type AlGaAs clad layer 4 sequentially stacked on a GaAs substrate 1. A current preventive layer 5 is formed on a sidewall of the p-type AlGaAs clad layer 4. A p-type GaAs cap layer 6 is stacked on the p-type AlGaAs clad layer 4 and the current preventive layer 5. An n-type metal layer 7 is formed below the GaAs substrate 1. A p-type metal layer 8 is formed on the p-type cap layer 6. The semiconductor laser diodes each having the aforementioned construction are aligned to form a chip bar for the semiconductor laser diodes.
Laser beams irradiated from the active layer 3 are used to read/write data from/to CD-RW or DVD. However, as the power of the semiconductor laser diode increases, catastrophic optical damage (COD) generated in the facet is on the rise as a serious problem.
The catastrophic optical damage is generated when there exists a defect in the facet or when the laser beam generated from the active layer 3 is not sufficiently reflected on the facet and is absorbed, so that the laser beam is converted into heat and the heat increases the power of the semiconductor laser diode. If the power of the semiconductor laser diode is increased, more amount of laser beam is absorbed in the facet, so that the semiconductor laser diode is damaged within a short time.
In order to prevent the aforementioned catastrophic optical damage, various methods were tried but these methods cause new problems.
As a first example, there is a method in which sulfur treatment is carried out in the surface of the facet. However, this method causes a contamination due to the use of wet process.
As a second example, the non-absorbing layer is made of a material having an energy band gap greater than that of the active layer to effectively restrain the COD. However, in order to increase the energy band gap by using an impurity, it is necessary to use dimethyl zinc in gas status as a main component. Also, in order to diffuse impurities only into a desired portion, the mask layer is essentially needed. As a result, since the number of the added processes increases, the method is disadvantageous in the aspect of the fabrication efficiency.